1. Field of the Invention
This invention relates to triarylphosphine and triarylphosphorane silver halide stabilizer precursors in heat stabilizable photographic silver halide materials. It also relates to processes of stabilization of heat stabilizable photographic silver halide materials by means of such stabilizer precursors.
2. Description of the State of the Art
Phosphorous compounds have been described in photographic silver halide materials as additives, such as antifoggants. This is described in, for instance, U.S. Pat. No. 3,951,661. These phosphorous compounds are phosphonium compounds, not phosphines or phosphoranes.
Silver halide stabilizer precursors have been described in heat stabilizable silver halide photographic materials. These stabilizer precursors are described in, for instance, Research Disclosure, June 1978, Item No. 17029. Stabilizers and stabilizer precursors described in heat stabilizable silver halide photographic materials are almost all sulfur compounds, not phosphorous compounds. It has been desirable to provide phosphorous compounds that enable improved stability of silver halide sensitization at low levels of stabilizer compared to sulfur compounds. No answer to the problem of what phosphorous compound is useful to replace a sulfur compound silver halide stabilizer precursor is found in the art.
The term "material" herein, such as in "photographic silver halide material", refers to photographic elements and photographic compositions. For instance, the term "heat stabilizable photographic silver halide material" refers to photographic elements and photographic compositions that are heat stabilizable.